Manual browser: log(3)
|LOG(3)||Library Functions Manual||LOG(3)|
NAMElog, logf, log10, log10f, log1p, log1pf log2, log2f, — logarithm functions
LIBRARYMath Library (libm, -lm)
DESCRIPTIONThe following functions compute logarithms:
- The log() and logf() functions return the natural logarithm.
- The log10() and log10f() functions return the base 10 logarithm.
- The log1p() and log1pf() functions return the natural logarithm of (1.0 + x) accurately even for very small values of x.
- The log2() and log2f() functions return the base 2 logarithm.
RETURN VALUESUpon successful completion, the functions return the logarithm of x as descibed above. Otherwise the following may occur:
- If x is NaN, all functions return NaN.
- If x is positive infinity, all functions return x. If x is negative infinity, all functions return NaN.
- If x is +0.0 or -0.0, the log(), log10(), and log2() families return either -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, whereas the log1p() family returns x.
- If x is +1.0, the log(), log10(), and log2() families return +0.0. If x is -1.0, the log1p() family returns -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL.
In addition, on a VAX, errno is set to EDOM and the reserved operand is returned by log() unless x > 0, by log1p() unless x > -1.
STANDARDSThe described functions conform to ISO/IEC 9899:1999 (“ISO C99”).
HISTORYThe history of the logarithm functions dates back to Version 6 AT&T UNIX.
|September 13, 2011||NetBSD 7.0|